The present invention relates to a device for conveying products.
In particular, the present invention relates to a device for conveying products of substantially elongated appearance advancing continuously and spaced equidistantly along a predetermined path. Reference is made in the following specification to a product typical of this broad description albeit no limitation in scope is implied.
Indeed whilst reference is made specifically to a device for conveying absorbent pads, as utilized in sanitary towels or napkins, the principles of the disclosure might be applied equally well to other products of substantially elongated shape, such as edible commodities.
Conventionally, such conveying devices operate on lines along which products, spaced apart initially at a first pitch P1, are caused to advance at a first velocity V1 before being spaced apart at a second pitch P2 different to the first and directed thus toward a further machine unit at a different velocity V2.
To bring about the change, such conveying devices will generally comprise an infeed and an outfeed conveyor extending along a predetermined feed path, also a transfer head disposed partly between the two conveyors, rotatable about an axis disposed orthogonally to the feed path and carrying a set of handler units furnished with respective uplifters by which the products are picked up cyclically and transferred from the one conveyor to the other in such a way that their position in space is changed during the course of the transfer. This is achieved conventionally by incorporating an epicyclic drive train into the transfer head, through the agency of which the handler units are made to advance along a substantially annular looped trajectory exhibiting rounded vertexes with a relatively short radius of curvature, and substantially rectilinear stretches interconnecting each two contiguous vertices. More exactly, two such contiguous vertices of the looped trajectory are disposed respectively above an exit end of the infeed conveyor and above the entry end of the outfeed conveyor, compassing a portion of the path along which the products are transferred and repositioned in space.
In general, the handler units are equipped with means by which the respective uplifters are driven and rotated; these consist typically in mechanical linkages containing higher pairs and mechanisms with cam profiles of which the functions, generated by uniform rotation of the transfer head, are to translate the uplifters toward and away from the feed path in such a way as to pick up and release the products, and to rotate the selfsame uplifters about the axis of translation so as to vary the position in space of the products during their transfer from one conveyor to the other, according to a predetermined law of motion.
It will be clear that whilst the angular velocity of the transfer head remains constant, the linear velocity of the handler units as they follow the looped trajectory is discontinuous. More precisely, the translational velocity of the handler units as projected along the direction of the aforementioned predetermined feed path is variable, decreasing to minimum values at the two contiguous vertices and reaching a maximum value at an intermediate point along the portion of the trajectory located above the feed path and between the same two vertices.
During operation of the device, therefore, it is important that the movements of the handler units are timed with due precision in relation to the two conveyors, in such a manner that the pickup of the single product from the infeed conveyor occurs at a point on the path situated in the neighbourhood of the first vertex of the feed trajectory and at a distance from this same vertex coinciding with a moment when the linear velocity of the handler unit is instantaneously identical or at least closely approximate to the feed velocity V1 of the infeed conveyor beneath. A similar condition applies for the release of the product, which must occur at a point on the path situated in the neighbourhood of the second vertex and at a distance from this same vertex coinciding with a moment when the linear velocity of the handler unit is instantaneously identical or at least closely approximate to the feed velocity of the outfeed conveyor, otherwise the pitch and the correct position in space will be lost.
This requirement is highlighted especially in the case of products, such as absorbent pads (sanitary towels or napkins), exhibiting a substantially rectangular geometry typified by a predominating longitudinal dimension considerably greater than the transverse; in this instance, it happens that when the single product is rotated through 90.degree. or thereabouts, the two feed pitches P1 and P2 and the velocities V1 and V2 of the two conveyors differ one from another by relatively significant amounts. As a result, the distance of the pickup point from the first vertex will be different to the distance of the release point from the second vertex.
It will be evident from the preamble that with predetermined mechanical ratios existing between the linkages through which motion is transmitted to the transfer head carrying the handler units, and the linkages transmitting linear and angular motion to the relative uplifters, conveying devices of the conventional type in question are unable to respond as desired to variations in position of the pickup and release points with respect to the infeed and outfeed conveyors. Thus, one has a certain lack of flexibility as regards the capacity of the device to adapt swiftly to variations in the dimensions of the products and/or to variations in the operating speeds of the infeed and outfeed conveyors along the feed path, and therefore to changes in the size of the products being conveyed.
The object of the present invention is to provide a conveying device such as will allow of picking up and releasing products at desired velocities and pitches, also of adjusting the pickup and release operations in such a way that these same operations can be timed to occur at different points along a given feed path, and in general overcoming the problems outlined above with reference to the prior art.